Posts Tagged 'egg'

All things considered, dinosaur embryos are not actually that rare. The issue with many however, is working out what taxon they might belong to. After all, a very young ceratopsian is not going to have much of a crest or horns which is generally how we identify them. In fact the skull is often the weakest and most disintegrated part of even a great embryo and as such quite a few are left as simply ‘indet’ on their designations. This is, sadly, another one, but the identification is quite specific – it belongs to a therizinosaur. These are not especially common taxa and aside from this. I’m not aware of any other eggs assigned to the group which makes one with an embryo in rather special.

Of course there’s not too much to see here, the bones are tiny and (shooting through glass a distance away) it’s not the greatest of photos. Still, it is nice to see just what detail can preserve on occasion, and if you look carefully, you should be able to see an associated premaxilla and maxilla that make up the snout and outline the naris and antorbital fenestra. Cool!

Many of you may have seen this already, but a new paper is out with what can only be described as a female pterosaur. This is big news, while there have been suggestions in the literature (most notably about Pteranodon) about some specimens representing males or females, this is one rather more convincing than many for the simple reason that there is an egg associated with it. That it is another Darwinopterus and a great specimen too, only adds to the interest.

The egg, sadly, lacks any trace of an embryo (though this is perhaps not surprising as obviously the egg was only about to be laid, not about to hatch) but has all the characteristics of pterosaur eggs and is the right size and shape. It also lies between the legs of the female and just behind the pelvis. That it is not in the body is not a major issue – a similar situation is commonly seen with icthyosaurs for example where decomposition leads to bloating of the body and forces out anything large and solid like a late term embryo or as in this case, and egg that’s ready to be laid.

Oddly enough the real interest in the paper lies in the head of the animal. The egg clearly points to this being a female but the head has no trace of a crest, despite other specimens of Darwinopterus having one (as you can see here for example). The strong suggestion therefore is that Darwinopterus is sexually dimorphic with males having crests and females none. The authors make a pretty good case, though a hatful of other specimens with other consistent differences in something approaching a 50:50 split would be better still.

One note of warning I would add though, is not to take this too far. Such extrapolation is fine for Darwinopterus, but I’d be very wary of taking the same basic criterion and applying it to other pterosaurs. Just as a quick example, many antelope and bovids have horns in males and females, and some can be nearly identical between the two, and in reindeer the females have antlers for parts of the year when males have none, while in most deer of course only males present antlers. I suspect it’s a matter of days before we see the first crested pterosaur specimen = male (or no crest = female) blog posts or media reports but this would be, for me, a very big assumption too far. A great start yes, but not even the end of the beginning for pterosaur dimoprhism.